Final answer:
Blood within vessels flows in layers called laminae, with the fastest flow in the center. Flow is affected by pressure gradients, vessel diameter, friction, and other factors, rather than just heart rate.
Step-by-step explanation:
The question "When blood flows through the blood vessel it can best be described as behaving how?" relates to the behavior of blood flow within the circulatory system. In reality, blood flows through vessels in concentric layers known as laminae, with the flow rate being the greatest near the center of the vessels. This is due to the phenomenon of laminar flow, where the blood close to the wall of the blood vessels moves more slowly due to friction, whereas the blood in the center moves more quickly because it experiences less friction.
The blood flow is not determined solely by the heart rate, and the idea that blood flows at the exact same rate throughout the closed circulatory system is incorrect. Factors such as vessel diameter, blood viscosity, overall combined diameter of capillaries, and the pressure gradients generated by the pumping heart affect the flow rate. Notably, in capillaries, the flow is slower to facilitate gas and nutrient exchange, and in veins, the flow is aided by valves preventing backflow and by muscle contractions.